Quantum88
I'm sorry if this forum has a search function and I'm not using it.. because I'm guessing this has been discussed, however I have a specific example I can't get out of my mind and I need to ask someone who knows... here it is...

546 that's the number... now this needs to be made into two sig figs in scientific notation. so 5.46 times 10 to the second. 546 itself does not by any means round to 600 so it couldn't be 600 that way... but 5.46 does round to 5.5 which rounds up so it could b e 6.0 times 10 to the second right? My physics teacher knows what he's doing but he sucks at explaining things.
steveswin
Significant Figures:

3 1 sig fig
3.1 2 sig fig
3.142 4 sig fig

The rules for significant figures are as follows:

1. Leading zeros are never significant.
2. Imbedded zeros are always significant.
3. Trailing zeros are significant only if the decimal point is specified.

Examples:

0.045 2 sig figs
2.095 4 sig figs
250 2 sig figs
250. 3 sig figs

Converting to scientific notation always helps!!

So 546

546 in scientific notation is 5.46 x 10^2 (3 sig figs)
5.46 x 10^2 is 5.5 x 10^2 (2 sig figs, rounded up)

Hope that helps.

regards

14159
You should only round once. (5.46 --> 5.5, but don't round 5.5 to 6)
Quantum88
Well on this particular test we got an "answer sheet" and 6.0 x 10^2 was the closest thing I had to choose.. it's only a high school class basically and most people don't care enough to question it... I didn't bother because the teacher really never seems to get your questions when you ask, he's a little up in years... knows what he's doing though.. just sometimes...

By the way is 6.0 x 10^2 two sig figs, the trailing decimal after the zero is a sig fig right?
steveswin
6.0 x 10^2 is to 2 sig figs because of the decimal point.
I still feel that the more correct answer is 5.5 x 10^2 as you loose the accuracy if you round further. You should only round down once.
Quantum88
Yes I feel the same way, but for some reason it wasn't an available answer on the test. I checked and double checked the rather simple math, made me feel like an idiot how long I took on that test.
Isaac
Are good quality figs
PhysOrg scientific forums are totally dedicated to science, physics, and technology. Besides topical forums such as nanotechnology, quantum physics, silicon and III-V technology, applied physics, materials, space and others, you can also join our news and publications discussions. We also provide an off-topic forum category. If you need specific help on a scientific problem or have a question related to physics or technology, visit the PhysOrg Forums. Here you’ll find experts from various fields online every day.